pic: 1726 week 4

[TheOtherGuy]

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[DarkFlame145]

Very cool looking, I like the chain system on it.

[falconmaster]

You beat us on the chassis weight, we were 70-75!

[AdamHeard]

Why not use two idlers rather than the curved plastic? It'd be a lot more efficient.

[TheOtherGuy]

The green plastic is our tensioner. The hole is off center, so we just loosen it and rotate it to tension the chain.

[MrForbes]

Originally Posted by AdamHeard

Why not use two idlers rather than the curved plastic? It'd be a lot more efficient.

I'm curious how we'd calculate the efficiency of it either way...any ideas?

[GUI]

Originally Posted by AdamHeard

Why not use two idlers rather than the curved plastic? It'd be a lot more efficient.

The curved plastic is UHMW Polyethylene chain guide from McMaster. It is very light and has very little friction on the chain. Using idlers would have placed the top length of the chain a lot higher up from the frame, and would have been very difficult to mount.

[Matt H.]

I'd say the efficiency loss due to friction on the plastic is minimal and worth the benefit of not having to make very precise holes for idlers. As a general team moto the less machining the better.

[Gdeaver]

Why the AL frame. You're using poltrusion below. Why not continue with the uper frame?

[Matt H.]

The Al is for mounting the mechanism on it--it save weight (lots) and is easier to machine than pultrusion. Pultrusion must also be thicker to achieve the same strength as aluminum so it would be unwieldy to mount that way.

[MrForbes]

or, the short answer: we had the pultruded fiberglass channel for the frame already, but no thin angle, so we went with aluminum. Also the aluminum is available at Ace hardware, and easy to replace if it we have problems with it in competition.

[falconmaster]

Originally Posted by Gdeaver

Why the AL frame. You're using poltrusion below. Why not continue with the uper frame?

Yes! As a pioneer of Pultruded Fiberglass in FIRST I would like to know why too!

[CCCP]

our bot is so cool

[MrForbes]

We like to play around with different materials, finding the best material for each part, kind of as an engineering exercise. A lot of that has to do with the equipment we have available in the shop, time needed to order materials and build parts, as well as the loading on each part. I think fiberglass is really excellent for frames, but it is a bit more tricky to use it in the upper parts of the robot, and we haven't gotten good enough at designing with it yet to feel confident using it there.

[BHS_STopping]

Originally Posted by CCCP

our bot is so cool

I'm sure the rest of the team is proud of it too, Stan.